Energy attenuation device for a fluid-conveying line and method of attenuating energy in such a line

ABSTRACT

An energy attenuation device for a fluid-conveying line, and a method for attenuating energy in such a line, are provided. The device includes one or more hose sections disposed in the fluid-conveying line, and at least one spring disposed in at least a portion of each of the hose sections.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a new energy attenuation device for afluid-conveying line and to a method of attenuating energy in such aline. The invention is particularly suitable for placement in thehydraulic system of a power steering unit of a vehicle, although theinvention would also be suitable for any other fluid-conveying system.

2. Prior Art Statement

In hydraulic systems where the operating fluid is circulated by a pump,the pulsations of pressure that are generated by the pump aretransmitted through the conduits and result in noise and/or vibrationbeing produced by the hydraulic fluid. In the case of power steeringfluid in vehicles, such noise and/or vibration is caused, for example,when vehicles are being parked or unparked at idle or very low speeds ofmovement thereof, such as barely moving into and out of a parking spaceor the like while the wheels of the vehicle are being turned by thepower steering mechanism thereof. In particular, substantial noiseand/or vibration (shutter) can be produced in such a situation when thepower steering fluid passes through the power steering mechanism fromthe fluid pump to the effective steering structure. Further backgroundin this area can be obtained from U.S. Pat. No. 3,323,305, Klees,whereby this U.S. Patent is being incorporated into this disclosure bythis reference thereto.

Systems are known for controlling the resonation of pressure waves infuel injection systems. For example, U.S. Pat. No. 5,168,855, Stone,passes fluid through check valves that are provided with a flowrestriction either directly therein or in a bypass line. U.S. Pat. No.5,509,391, DeGroot, provides a spool valve assembly for controlling flowbetween inlet and outlet ports.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide animproved device and method for attenuating energy in a system thatconveys fluid.

This object is realized pursuant to the energy attenuation device of thepresent invention by providing a hose section disposed in afluid-conveying line, and disposing a spring in at least a portion ofthe hose section.

Accordingly, it is an object of this invention to provide a novel energyattenuation device having one or more of the novel features of thisinvention as set forth above or hereinafter shown or described.

Another object of this invention is to provide a new method ofattenuating energy in a fluid-conveying line, the method of thisinvention having one or more of the novel features of this invention asset forth above or hereinafter shown or described.

Other objects, uses and advantages of this invention are apparent from areading of the specification in conjunction with the accompanyingschematic drawings, which form a part thereof and wherein:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a simplified automotive power steering system that isdesigned to incorporate the energy attenuation device of this invention;

FIG. 2 shows one exemplary embodiment of the energy attenuation deviceof this invention;

FIG. 3 illustrates, partially in cross-section, another exemplaryembodiment of the energy attenuation device of this invention;

FIG. 4 shows one exemplary embodiment of the spring of the energyattenuation device of this invention;

FIGS. 5-8 are views similar to that of FIG. 3 showing further exemplaryembodiments of the energy attenuation device of this invention;

FIGS. 9 and 10 are exemplary embodiments showing the energy attenuationdevice of this invention in return lines of power steering systems;

FIG. 11 is a graph showing large migrations or spikes of vibration inthe return line of a power steering system that does not incorporate theenergy attenuation device of the present invention; and

FIG. 12 is a graph showing significantly reduced vibration in a returnline of a power steering system that has incorporated the inventiveenergy attenuation device therein.

DESCRIPTION OF PREFERRED EMBODIMENTS

While the various features of this invention are hereinafter illustratedand described as providing an energy or sound attenuation apparatus foran automotive power steering system, it is to be understood that thevarious features of this invention can be utilized singly or in variouscombinations thereof to provide an energy attenuation apparatus forother systems that convey fluid.

Therefore, this invention is not to be limited to only the embodimentsillustrated in the drawings, because the drawings are merely utilized toillustrate one of the wide variety of uses of this invention.

Referring now to the drawings in detail, FIG. 1 illustrates a simplifiedautomotive power steering system. During operation, the power steeringpump 11 generates pressure ripples that are transmitted through tubingT, such as steel tubing, to the pressure hose assembly or pressure line12, the power steering gear 13, the return hose assembly or return line14, and the reservoir 15, and finally flow back to the pump 11 itself bymeans of the supply line 16. It should be noted that rather than beingseparated by a hose or similar conduit, the reservoir 15 and the pump 11could actually be a single unit.

In order to greatly reduce noise, such as from resonance, especially inthe return line 14, and thereby eliminate or at least greatly reduce thepower steering noise or vibration generated by the power steering pump11, the energy attenuation device of this invention, which is generallyindicated by the reference numeral 20, is disposed in the return line 14between the gear 13 and the reservoir 15 or the pump 11. Alternatively,it would also be conceivable to dispose the energy attenuation device 20in the pressure line 12, or in both the return line 14 and the pressureline 12. Various exemplary embodiments of the energy attenuation device20 and components and arrangements thereof are illustrated in FIGS.2-10, and will be described in detail subsequently.

One exemplary embodiment of the energy attenuation device 20 of thisinvention is shown in FIG. 2, and comprises a spring 21 that isdisposed, for example, in the return line 14 or the pressure line 12 ofthe system of FIG. 1, although the spring 21 can also be disposed in aseparate hose section that is in turn disposed in such return line 14 orpressure line 12, as illustrated in the exemplary embodiments of FIGS. 3and 5-8, where the spring 21 is shown disposed in a hose section 22.

FIG. 10 illustrates how the inventive energy attenuation device 20 isdisposed in a return line 14 or separate hose section 22 provided in areturn line 14 of a power steering system, with the return line 14 orhose section 22 leading to an optional filter element 24. As can be seenin this embodiment of an actual segment of a return line 14 of a powersteering system, the spring 21 does not extend throughout the entirelength of the return line 14 or hose section 22. Rather, the spring 21is permitted to freely float in the hose section, thus centering itself,or coming to rest at one end of the hose section, as fluid flows throughthe system. Although the other illustrated embodiments, which areprovided for the purpose of showing various alternative arrangements,show the spring 21 as occupying most if not all of a given hose section22, in reality such springs 21 would probably not extend throughout theentire length of the hose section but rather would have a configurationsimilar to that shown in FIG. 10.

In the embodiment illustrated in FIG. 3, a hose section 22, which is,for example, a flexible hose made of rubber or other elastomericmaterial, is disposed between two tubing members T, with each end of thehose section 22 being connected to a respective tubing member by meansof a coupling 25. The movement of the spring 21 within the hose section22 can be limited in any suitable manner, such as by the provision of awasher 26 at one or both ends of the hose section 22, or at any othersuitable location in the hose section. The couplings 25 themselves canalso be used to limit the movement of the spring 21, as shown, forexample, in the embodiments of FIGS. 5-8. In addition, the hose section22 could be molded directly to the spring 21, in which case the springwould have a diameter that is actually slightly greater than the innerdiameter of the hose section. However, as indicated previously, it ispresently preferred that the spring 21 be allowed to float freely withinthe hose section 22.

As indicated previously, especially in conjunction with FIG. 10, thespring 21 is expediently of such a length that it will not extend overthe entire length of the hose section 22. Such a spring 21 could,however, extend over the entire length of the hose section 22, extendover a substantial portion thereof, or extend over only a short portionof the length of the hose section 22. If fixed within the hose section22, a spring 21 that does not extend over the entire length thereofcould be fixed in position at any suitable location thereof.Furthermore, more than one spring 21 could be disposed in the returnline 14 or pressure line 12. For example, FIG. 8 shows an embodimentwherein a first spring 21 is disposed in the hose section 22, and afurther spring 21′ is disposed in a second hose section 22′. In thisembodiment, the two springs 21, 21′ are separated from one another by afurther hose section 28″ as will be described in detail subsequently.

The inventive energy attenuation device 20 can also be used inconjunction with a steel cable device, such as the ¼ wave steel cabledevice 30 of FIGS. 6 and 8, or with a device such as that shown in FIG.7. In the device of FIGS. 6 and 8 a steel cable 30 is disposed in afurther hose section 31 and 28 respectively that is interconnected tothe hose section 22 and 22′ by means of a further coupling 25. Thedevice of FIG. 7 differs from that of FIG. 6 in that rather than beingprovided with a steel cable, a cable 30′ made of plastic, such asTeflon, is provided. In this embodiment, the plastic cable 30′ isprovided with holes 32. In the embodiment of FIG. 8, the further hosesection 28, in which is disposed the cable 30, which could either be asteel cable or a plastic cable as shown in FIG. 7, is disposed betweentwo hose sections 22, 22′ that contain a spring 21, 21′ respectively,with the hose section 28 being interconnected with the hose sections 22and 22′ via couplings 25.

It should furthermore be noted that the inventive energy attenuationdevice 20, with its spring 21 in a hose section 22, can be used inconjunction with a variety of heretofore known sound and vibrationattenuation devices in addition to the cable means shown in FIGS. 6-8,with such heretofore known devices including additional chambers andadded hose sections. For example, reference is made to U.S. Pat. Nos.4,611,633 (Buchholz et al) , 5,172,729 (Vantellini) and 5,201,343(Zimmermann et al), whereby such U.S. Patents are being incorporatedinto this disclosure by this reference thereto. FIG. 9 illustrates afurther working embodiment of the energy attenuation device 20 of thepresent invention as disposed in a return line 14.

It is to be understood that the characteristics, such as length,thickness, tension, number of coils per inch, etc., of the spring 21 ofthe inventive energy attenuation device 20 can vary in conformity withexisting requirements. In addition, this spring can be made of anysuitable material, such as metal, especially stainless steel, orplastic. For example, one exemplary embodiment of a spring 21 isillustrated in FIG. 4. This spring is made of stainless steel, and istherefore particularly suitable for the environment of power steeringfluid. This particular spring is designed to have six coils per inch,with an outer diameter of approximately 0.86 cm (0.34 inches), with thewire of the spring itself having a thickness of about 0.061 cm (0.024inches). As indicated above, the characteristics of the spring willdepend upon a particular pump application. Thus, any of the exemplaryembodiments illustrated in the drawings can have different diameters andsizes of both the hose sections and the springs.

As indicated previously, the pressure pulses resulting from therevolutions of a pump create vibrations and noise. This phenomena, alongwith the significant improvement provided by the inventive energyattenuation device, are illustrated in FIGS. 11 and 12 whereinvibrations measured in m/s² are plotted versus real time. In particular,from the vibration measurement shown in FIG. 11 at the tie rod end of apower steering system that is not provided with the inventive energyattenuation device, very large migrations of the generated vibrationscan be seen. In contrast thereto, in the graph shown in FIG. 12 of thevibration situation as it exists downstream of an inventive energyattenuation device inserted into the return line of a power steeringsystem, no large spikes or migrations can be seen in the curve, which isa sign wave having low amplitude vibrations.

In view of the foregoing, it can be seen that this invention not onlyprovides a new energy attenuation device, but also this inventionprovides a new method for attenuating energy in a fluid conveyingsystem.

While the forms and methods of this invention now preferred have beenillustrated and described as required by the Patent Statute, it is to beunderstood that other forms and method steps can be utilized and stillfall within the scope of the appended claims, whereby it is believedthat each claim sets forth a novel, useful and unobvious inventionwithin the pervue of the Patent Statute.

1. An energy attenuation device for a liquid-conveying line, comprising:a hose section disposed in said liquid-conveying line; and a firstspring disposed in an at least partially non-embedded manner within atleast a portion of said hose section and not extending beyond said hosesection, wherein said spring provides energy attenuation for liquid thatis being conveyed through said liquid-conveying line.
 2. An energyattenuation device as set forth in claim 1, wherein at least a portionof an outer diameter of said spring is slightly greater than an innerdiameter of said hose section such that said greater diameter portion iswedged against but not embedded in said hose section.
 3. An energyattenuation device as set forth in claim 2, wherein said greaterdiameter portion is disposed in an end section or anywhere along thelength of said spring.
 4. An energy attenuation device as set forth inclaim 1, wherein a portion of the length of said spring is embedded insaid hose section.
 5. An energy attenuation device as set forth in claim4, wherein said embedded portion is an end section or anywhere along thelength of said spring.